1. Field of the Invention
The present invention relates to an image forming apparatus such as a copier or a printer, and more particularly to a paper feed control technique for selectively feeding paper to an image forming section.
2. Description of the Related Art
In an image forming apparatus such as a copier or a printer, the number of times a paper tray needs to be replenished with paper can be reduced and the available time of the apparatus improved by equipping the apparatus with a large capacity paper tray or a number of paper trays. For example, Japanese Unexamined Patent Publication JP-A 7-219401 (1995) discloses a technique for shortening the first copy time by mounting two paper trays in the same supporting member, both accommodating the same size paper, and by feeding at least the first sheet of paper out of the paper tray mounted nearer to the image forming section and subsequent sheets out of the paper tray mounted farther from the image forming section.
In the technique disclosed in JP-A 7-219401, in order to shorten the first copy time, a number of sheets of paper, including the first sheet, are always fed out of the paper accommodating section whose paper transport distance to the image forming section is the shortest. However, after accommodating the same size paper into a plurality of paper accommodating sections mounted in the same supporting member and constructed so as to be drawn out as a single unit, or into a plurality of paper accommodating sections mounted in separate supporting members and constructed so as to be drawn out separately, if a number of sheets of paper, including the first sheet, have to be fed out of the paper accommodating section whose paper transport distance to the image forming section is the shortest, as described above, a situation can occur where even when any one of the other paper accommodating sections mounted farther from the image forming section is ready to feed paper, the operation has to wait until the paper accommodating section whose paper transport distance to the image forming section is the shortest gets ready to feed paper, and this leads to the problem that the first copy time becomes correspondingly longer.
This problem becomes particularly apparent in the case of an image forming apparatus equipped with a large capacity paper accommodating section. For example, consider the case where the large capacity paper accommodating section ran out of paper and the user replenished the paper accommodating section with paper, but not up to the maximum capacity of it, because he was in a hurry. In this case, if the paper accommodating section replenished with paper happens to be the one whose paper transport distance to the image forming section is the shortest, the time required for the paper accommodating section to move up and get ready for paper feed after the paper replenishment may be longer than the difference between the time that would be required to transport paper from that paper accommodating section to the image forming section and the time that would be required to transport paper to the image forming section from some other paper accommodating section having a longer paper transport distance to the image forming section.
In that case, with the technique described in JP-A 7-219401, since a number of sheets of paper, including the first sheet, are always fed out of the paper accommodating section whose paper transport distance to the image forming section is the shortest, there remains the problem that the first copy time becomes longer by the time required for that (large capacity) paper accommodating section to get ready for paper feed, as described above.
An object of the invention is to provide an image forming apparatus capable of paper feed control that can reduce the first copy time as much as possible when there is more than one paper tray that holds the same size paper.
The invention provides an image forming apparatus comprising:
an image forming section for forming an image on paper;
a first paper accommodating section for accommodating therein prescribed size paper specified to be fed to the image forming section, the first paper accommodating section being movable between a paper replenishment position where paper can be replenished, and a paper feed position where the paper is ready to be fed out;
a second paper accommodating section for accommodating therein paper of the same size as the paper held in the first paper accommodating section, the second paper accommodating section being movable between a paper replenishment position where paper can be replenished, and a paper feed position where the paper is ready to be fed out, and requiring a longer time than that of the first paper accommodating section to transport the paper to the image forming section;
paper feed means, provided for each of the paper accommodating sections, for feeding the paper placed in the paper accommodating sections to the image forming section one sheet of paper at a time; and
a paper feed control section for performing control in such a manner that when setting each of the first and second paper accommodating sections from the paper replenishment position to the paper feed position, in the case where one of the paper accommodating sections has been set into the paper feed position earlier than the other paper accommodating section, paper feed is started from the paper accommodating section that has been set into the paper feed position earlier.
In the invention, the paper feed control section performs control in such a manner that when setting each of the first and second paper accommodating sections from the paper replenishment position to the paper feed position, in the case where the first paper accommodating section has been set into the paper feed position earlier than the second paper accommodating section, paper feed is first started from the first paper accommodating section, and after the second paper accommodating section has been set into the paper feed position and become ready to feed paper following the paper being fed out of the first paper accommodating section, paper feed from the first paper accommodating section is stopped and paper feed from the second paper accommodating section is started.
In the invention, the paper feed control section performs control in such a manner that when setting each of the first and second paper accommodating sections from the paper replenishment position to the paper feed position, in the case where the second paper accommodating section has been set into the paper feed position earlier than the first paper accommodating section, paper feed is first started from the second paper accommodating section, and after the first paper accommodating section has been set into the paper feed position and become ready to feed paper following the paper being fed out of the second paper accommodating section, paper feed from the second paper accommodating section is stopped and paper feed from the first paper accommodating section is started.
According to the invention, the first copy time is prevented from becoming longer due to the time difference occurring when setting each of the first and second paper accommodating sections from the paper replenishment position to the paper feed position, and also, the paper consumption in the paper accommodating section whose paper transport time to the image forming section is shorter is reduced, thereby increasing the opportunity of being able to shorten the first copy time, while at the same time, substantially equalizing the cumulative number of sheets handled by the paper feed means between the two paper accommodating sections so that both paper feed means can be replaced at a time.
The invention also provides an image forming apparatus comprising:
an image forming section for forming an image on paper;
a first paper accommodating section for accommodating therein prescribed size paper specified to be fed to the image forming section, the first paper accommodating section being movable between a paper replenishment position where paper can be replenished, and a paper feed position where the paper is ready to be fed out;
a second paper accommodating section for accommodating therein paper of the same size as the paper held in the first paper accommodating section, the second paper accommodating section being movable between a paper replenishment position where paper can be replenished, and a paper feed position where the paper is ready to be fed out, and requiring a longer time than that of the first paper accommodating section to transport the paper to the image forming section;
paper feed means, provided for each of the paper accommodating sections, for feeding the paper placed in the paper accommodating section to the image forming section one sheet of paper at a time; and
a paper feed control section for performing control in such a manner that when feeding paper from the second paper accommodating section to the image forming section, in the case where the second paper accommodating section runs out of paper, an indication is produced signaling the need to replenish the second paper accommodating section with paper, while at the same time, paper is fed out of the first paper accommodating section, following the paper fed out of the second paper accommodating section, and
thereafter, when the second paper accommodating section has been replenished with paper, and when the second paper accommodating section has been set into the paper feed position and become ready to feed paper following the paper being fed out of the first paper accommodating section, paper feed from the first paper accommodating section is stopped and paper feed from the second paper accommodating section is resumed.
According to the invention, when the second paper accommodating section needs to be replenished with paper, paper is fed out of the first paper accommodating section instead of the second paper accommodating section, and after the second paper accommodating section has been replenished with paper and become ready to feed paper following the paper being fed out of the first paper accommodating section, paper feed from the second paper accommodating section is resumed; as a result, not only can the paper consumption in the first paper accommodating section be reduced, but the image forming operation can be continued while the second paper accommodating section is being replenished with paper, and the print job can be completed without delay.